The present invention refers to a programmable decoder for irrigation plant, a programming procedure for said decoder and a centralized irrigation plant comprising a plurality of said decoders.
Automatic irrigation plants controlled by control systems or electronic units for the maintenance of lawns, gardens and other green areas are known.
There is an increasing need of remote controlled irrigation plants, as they enable construction and maintenance cost to be reduced.
These types of irrigation plants are divided into due main categories, that are: a) plants for short and medium distances from the control system, that have a limited number of solenoid valves to control; b) plants for long distances from the control system, that have a high number of solenoid valves to control.
In particular short and long distance irrigation plant control systems are already known, that make use of communication interfaces that enable the control systems programming parameters to be modified.
In addition specific methods for controlling the solenoid valves are already known and among these we can note in particular: a) control system connected by means of electric cables to each single solenoid valve as shown in FIG. 1, in which it can be seen that a control unit 1 is fed by means of a supply line 2 and said control unit 1 is connected at a distance xe2x80x9cdxe2x80x9d, by means of a plurality of electric cables 3, to each single solenoid valve 4, 5, . . . , 6; b) control system connected by means of radio frequency RF to each solenoid valve as shown in FIG. 2, in it can be seen that the control unit 1 is connected to supply line 2 and said control unit 1 is connected by means of an RF transmitting device 14 to respective receiving devices 7 belonging to each single solenoid valve 4, 5, . . . , 6; c) a system in which each solenoid valve is commanded by a control system independently from the other solenoid valves as shown in FIG. 3, in which a plurality of control units 8 can be noted which are fed from respective supplies 2 and said plurality of control units 8 are connected to respective solenoid valves 4, 5, . . . , 6; d) a central control system connected by means of one single pair of cables to all the solenoid valves as shown in FIG. 4, in which it can be seen that a control unit 9 is fed by the supply 2 and said control unit 9 is connected by means of one single pair of cables 10 to a complex of decoders 11, 12, . . . , 13xe2x80x94solenoid valves 15, 16, . . . , 17.
Each of these typologies is particularly adapted for a specific irrigation plant control system that is duly chosen by the engineer of the plant itself.
In specific reference to the case of the above-mentioned system (d), this will be widely used in the case of a long distance irrigation plant with a high number of solenoid valves and with centralized control.
Examples of this plant typology are, for example, irrigation plants along roads, in golf courses, large parks and vast geographic areas.
To command the opening/closing of the solenoid valves in the case of the above-mentioned system (d), it is known that devices such as decoders to encode/decode electrical signals from and to the control unit are added, which however increase installation and maintenance costs.
These decoder systems usually provide for a connection cable from the control system to the decoders themselves of the two-pole or three-pole type having a direct or alternating current input.
In turn the single decoder can drive the solenoid associated to each solenoid valve both in alternating and direct current. If it is usual, considering the very wide use of 24 VAC solenoids in using said typologies of solenoids, the use of a bistable type solenoid results more suitable as it requires power only when it activates and deactivates the valve and not for the entire period that the valve itself is open.
Therefore, using a 24 VAC solenoid the consumption of current needed to supply a plant that uses said solenoids, is considerably higher than that required by a plant that uses bistable type solenoids, under equal conditions.
As a result the section of the connection cable between the control unit and the decoders can be reduced, thus reducing the costs of said plants which for their nature are suitable for long distances between the control unit and the solenoid valves.
In addition the bistable solenoids, exactly for this characteristic of extremely low consumption, are more and more used in the irrigation section thus becoming just as common as the 24 VAC solenoids.
The operating principle of the decoder system is thus to guarantee to each decoder associated to each solenoid valve a minimum charging current for a long time so that once the decoder has been charged, it awaits the command from the control system to open or close the solenoid valve connected to it.
As in an irrigation plant there are hundreds of solenoid valves and the same number of decoders, each decoder is supplied a minimum current so as to guarantee limited losses in tension due to the considerable lengths of the supply cable.
This choice is appropriate as well as the supply cables have a smaller section with a considerate saving in cost.
From the electrical point of view, and still for the saving in cost, a two-pole cable is usually chosen even though this entails greater complexity of drive circuits and decodifying compared to a three-pole cable.
In addition, independently from the type of solenoid used 24 VAC or bistable, it is preferable to use alternating current between the control unit and the decoders so as to avoid problems of corrosion in the cable terminations on each single decoder.
However the present irrigation plants fitted with solenoid valves with decoder do not allow the control of the widest range of conditions linked to the operating of the single solenoid valvexe2x80x94decoder complex.
In addition the present irrigation plants do not permit any malfunctioning of the single decoders and/or solenoid valves to be recognized.
One of the problems that affect the known irrigation systems is that as the bistable solenoid is activated only in correspondence with the opening or closing command of the valve controlled by it, it occurs that, because of an electrical disturbance the command is lost.
This leads to the solenoid valve remaining open instead of closed or vice versa.
One technique used to obviate this problem consists of repeatedly sending the opening or closing command relating to the state of the solenoid valve. This results in all the decoders being addressed sequentially starting from the first to the last and so on, in continuation. In this manner as the number of the controlled decoders increases, the time between two successive addressings of the same decoder also increases.
In addition, at each addressing the decoder not only receives the command relating to its solenoid valve, but also sends to the control unit the state of the sensor associated to it. Therefore we have the situation in which the control unit could, reacting to the information relating to the state of the sensor, open or close the solenoid valve associated to it. This command however could be sent only in correspondence with the successive addressing, with the imaginable consequences and waste of time.
In view of the state of the technique described, the object of the present invention is to produce a centralized irrigation plant with decoders capable of obviating the previously explained problems.
In accordance with the present invention, this object is reached by means of a decoder comprising first terminals suitable for receiving a first electric signal from a control unit, second terminals suitable for exchanging electric signals with detecting means and third terminals suitable for commanding solenoids for activating solenoid valves, said first electric signal being filtered by filtering means and successively rectified by rectifying means and finally decoded by decoding means suitable for generating a second electric signal, characterized in that said decoder comprises also processing means and memorizing means, said processing means being directly connected to said memorizing means, said processing means being suitable for processing said second electric signal so as to exchange electric signals with said second terminals and command said third terminals, and said memorizing means being suitable for memorizing permanently the data present in said first electric signal.
In this manner a centralized irrigation plant can be produced characterized in that it comprises a control unit commanded by a user interface, said control unit being connected by means of an electric supply cable to a plurality of decoders, each of said decoders possessing above mentioned the characteristics.
In accordance with the invention a procedure for programming a decoder in accordance with the above mentioned characteristics has also been executed, characterized in that it provides for a programming step made up of a step sending an electric signal from a user interface by means of suitable connection means, said connection means being fitted with un communication protocol, said communication protocol being made up of a plurality of fields: a) a first field defined by a plurality of characters to feed and synchronize a specific decoder; b) a second field defined by a first preset number of bytes, said bytes being subdivided into a second number of nibbles, in which each nibble is represented by an ASCII character; c) a third field defined by a number representing the hierarchical order of transmission of said bytes.
Thanks to the present invention each decoder can be permanently identified with a reference number.
In addition thanks to the present invention the operating of the solenoid valvexe2x80x94decoder complex can be personalized in function of the specific needs.
In addition thanks to the present invention the operating of the entire irrigation system can be controlled.
In addition thanks to the present invention it is possible to intervene immediately on the programming of the solenoid valvexe2x80x94decoder complex.